Lighting systems are important navigational aids for aircrafts, boats, or other vehicles, in providing guidance, signaling, and demarcation functions therefore. Semiconductor light emitting devices such as light emitting diodes (LEDs) have been identified to be the replacement for the conventional incandescent lights that are employed in the current navigational systems. LEDs offer many advantages over incandescent lights, which are driving the adoption of same. These advantages include but are not limited to high energy efficiency, long lifetime, low maintenance cost, enhanced reliability and durability, as well as no lumen loss induced by filtering.
The following are some examples of the issued patents or published patent applications related to the LED navigational lighting apparatus.
U.S. Pat. No. 6,489,733 issued to Schmidt et al. discloses a multi-purpose lighting system for airports, roads or the like. The lighting system is composed of a group of incandescent or LED light sources and a central control unit to monitor and control the operation of the light sources through wired communication with the micro-controllers built in the light sources.
U.S. Pat. No. 6,902,291 issued to Rizkin et al. discloses an in-pavement directional LED luminaire, which utilizes multiple high flux LEDs having their temperature controlled by a thermoelectric cooling device, and a non-imaging beam transformer for the concentration and the direction of light.
U.S. Pat. No. 6,932,496 issued to Rizkin et al. discloses an LED-based elevated omnidirectional airfield lighting apparatus. A light transformer is used for directing part of the light emitted by an LED light source in a limited angle omnidirectional pattern with precalculated intensity distribution while the remaining emitted light is dispersed across a hemisphere.
U.S. Pat. No. 5,224,773 issued to Arimura discloses a beacon lantern that uses a plurality of LEDs as a light source. A cylindrical Fresnel lens with improved light transmission factor is used for converging the LED beams in the horizontal direction. The lens is made by rolling a sheet-like, fine prism-shaped linear Fresnel lens into a shape of a cylinder.
U.S. Pat. No. 6,048,083 issued to McDermott discloses a bent focal line electronic lighting device for use as a signal or illuminator. Light is created by a plurality of LED elements. An optical lens contoured to have multiple focal points is used for efficient LED light collection and projection.
Other patents or patent applications related to LED navigational lights include U.S. Pat. No. 6,354,714 to Rhodes, U.S. Pat. No. 6,753,762 to Jorba Gonzalez, U.S. Pat. No. 6,030,099 to McDermott, U.S. Pat. No. 7,021,801 to Mohacsi, U.S. Pat. No. 5,608,290 to Hutchisson, U.S. Pat. No. 6,464,373 to Petrick, U.S. Pat. No. 6,905,228 to Takeyasu et al., U.S. Pat. No. 6,543,911 to Rizkin et al., U.S. Pat. No. 6,086,220 to Lash et al., U.S. Pat. No. 6,168,294 to Erni et al., and U.S. patent application Nos. 2005/0110649 to Fredericks et al., and 2004/0095777 to Trenchard et al.
One problem facing the LED lighting apparatus is the relatively low brightness of the LED lights. Even with the recent development of LED technology, the brightness of a single LED chip still cannot match that of conventional incandescent or arc lamps. Thus an array of LEDs will generally be needed to produce a light intensity that meets the national or international standards, such as FAA, NOAA, ICAO, UK-CAA, and/or NATO standards for navigational lights. This is especially true for those runway edge lights, approach lights, and threshold/end lights that are commonly used in commercial or military airports. In another aspect, most standards require the navigational light beam to satisfy certain criteria in divergence angle, intensity distribution, elevation angle, etc. This places a significant challenge in regard to LED beam control because the LED array cannot be viewed as a point light source. In the above cited patents or patent applications, the light beam produced by the whole LED array is controlled by specially designed lenses or beam transformers, which are both complicated in structure and difficult to manufacture. More importantly, these specially designed lenses or beam transformers limit standardization and mass production, which are the two key factors in driving down the cost of a lighting apparatus.
Additionally, for some applications such as in certain military or emergency navigation applications, the lighting apparatus is required to be quickly deployable and reconfigurable as well as preferably possess infrared emission capability for night vision or thermal imaging based navigation. It is also desirable to have sensor units embedded in the lighting apparatus for automatically monitoring and controlling their operation according to environment conditions. None of the above cited patents or patent applications address these issues.
Therefore, there is a need for an improved LED lighting apparatus for navigational aids, in which the apparatus is modularly designed for efficient production, configuration, and installation, as well as for precise beam property control.